• Journal of Environmental Science International
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• v.29 no.1
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• pp.95-108
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• 2020

Silver nanoparticles were loaded onto g-C₃N₄ (CN) with a nanoroll-type morphology (Ag/CN) synthesized using a co-polymerization method for highly selective conversion of toxic nitrobenzene to industrially-valuable aminobenzene. Scanning electron microscopy and high-resolution transmission electron microscopy (HRTEM) images of Ag/CN revealed the generation of the nanoroll-type morphology of CN. Additionally, HRTEM analysis provided direct evidence of the generation of a Schottky barrier between Ag and CN in the Ag/CN nanohybrid. Photoluminescence analysis and photocurrent measurements suggested that the introduction of Ag into CN could minimize charge recombination rates, enhancing the mobility of electrons and holes to the surface of the photocatalyst. Compared to pristine CN, Ag/CN displayed much higher ability in the photocatalytic reduction of nitrobenzene to aminobenzene, underscoring the importance of Ag deposition on CN. The enhanced photocatalytic performance and photocurrent generation were primarily ascribed to the Schottky junction formed at the Ag/CN interface, greater visible-light absorption efficiency, and improved charge separation associated with the nanoroll morphology of CN. Ag would act as an electron sink/trapping center, enhancing the charge separation, and also serve as a good co-catalyst. Overall, the synergistic effects of these features of Ag/CN improved the photocatalytic conversion of nitrobenzene to aminobenzene.

• Journal of Korea Water Resources Association
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• v.51 no.11
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• pp.959-969
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• 2018

The aging water pipes induce various problems, such as water supply suspension due to breakage, insufficient water pressure, deterioration of water quality, damage by sink holes, and economic losses due to water leaks. However, it is impractical and almost impossible to repair and/or replace all deteriorated water pipes simultaneously. Hence, it is required to quantitatively evaluate the deterioration rate of individual pipes indirect way to determine the rehabilitation order of priority. In this study, ANN(Artificial Neural Network)-Clustering method is suggested as a new approach to assess and assort the water pipes. The proposed method has been applied to a water supply network of YG-county in Jeollanam-do. To assess the applicability of the model, the evaluation results were compared with the results of the Numerical Weighting Method (NWM), which is being currently utilized in practice. The assessment results are depicted in a water pipe map to intuitively grasp the degree of deterioration of the entire pipelines. The application results revealed that the proposed ANN-Clustering models can successfully assess the water pipe deterioration along with the conventional approach of NWM.

• Journal of the Korean Magnetics Society
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• v.20 no.2
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• pp.52-60
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• 2010

The changes of magnetic flux density distribution and the degree of magnetic anomaly on the ground surface by underground fracture zones and empty spaces had been investigated through the variations of the measuring heights. The magnetic flux density distributions were monitored for the ground surfaces of fracture zones, empty spaces and tunnels by fluxgate-type magnetometer. The fracture zones showed the magnetic anomaly with (+) and (-) peak-pairs in the magnetic flux distribution measured at 0.15 m height from the ground surface, and this anomaly disappeared at the height of 1.15 m. The underground empty spaces and tunnels showed the decrease of magnetic flux densities, where the degree of this density decrease diminished with the increase of the underground depth. And, the existence and size of underground empty spaces, such as tunnels and sink holes, could be monitored by the phenomena of this decreasing flux density.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.6
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• pp.224-239
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• 2018

Autonomous vehicles can significantly reduce accidents due to 'driver's carelessness', which occupies the majority of causes for traffic accidents, but they may fail to avoid traffic accidents due to unexpected situations, such as "trolley dilemma", vehicle defects and road defects. Therefore in situations Autonomous vehicles need to be made ethical choices. This study assumes that Autonomous vehicles can not avoid traffic accidents due to unexpected sink holes. In this situation, the traffic accident costs was analyzed for the ethical choices of Autonomous vehicles. In the process, Autonomous vehicles were made to choose one of three ethical choices : (1) Egoism with priority on passenger safety, (2) Deontology for minimizing human damages, (3) Utilitarianism with minimizing traffic accident costs. As a result of the analysis, egoism had the highest traffic accident costs, and deontology for minimizing human damages had the lowest traffic accident costs.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.3
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• pp.129-136
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• 2017

Geographic Information System The geographic information system (GIS) has been limited to the government and some public sectors. Recently, the market has been diversified by combining with other areas such as mobile and CRM (Customer Relationship Management). The development direction of GIS technology in the 21st century is Web GIS, 3D GIS, mobile GIS, LBS, etc. as general technology for GIS application system development and spatial information service. In this study, we developed a new concept marking nail (a marking nail with built - in intelligent storage memory device) from the function of simple positioning of a marking nail related to a previously used underground item,, Burial depth, pipe thickness, piping material, management agency, contractor, contact, etc.) and store it in DB server, if necessary.Make it available in the right place. Through this research, it is possible to prevent and minimize various accidents caused by irregular excavation works, etc., and to provide information for establishing countermeasures related to sink holes. In order to provide systematic and reliable information on underground burial management, it was proposed to input information conveniently in the field, and the purpose was to reduce the incidence of buried underground pipes absolutely.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.3
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• pp.57-62
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• 2020

Among the sewage pipes installed in Korea, the length of concrete pipes exceeding 20 years is 66,334 km (42.5%). Deteriorated concrete sewer pipes need to be repaired due to the leakage of internal sewage, which causes problems such as sink holes by expanding the cavity around the pipeline. In this study, we tried to apply anti-washout underwater mortar with ultra rapid hardening cement and segregation reducing agent to sewage pipe repair. As a result of the setting time test, the final set time was delayed by up to 172% by incorporating segregation reducing agent. In the test for measuring the degree of mortar segregation in water, it was measured at pH 12 or less under all mixing conditions. In addition, the suspension amount was measured to be 50 mg / l or less to satisfy the KCI-AD102 standard by incorporating a segregation reducing agent. In terms of the average value of mortar compressive strength, by incorporating segregation reducing agent, the strength of the specimens produced in air was more than 80% of that of the specimens produced in water. Conversely, the bond strengths of the specimens produced in water were measured to be higher than those of the specimens produced in air. Water resistance was evaluated by measuring water absorption and water permeability. Water absorption and water permeability were reduced by 42.6% and 36.6%, respectively, by mixing segregation reducing agent.